Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric...

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Expertise in Marine Hydrodynamics Hull form optimisation with Computational Fluid Dynamics Aurélien Drouet, Erwan Jacquin, Pierre-Michel Guilcher

Transcript of Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric...

Page 1: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

Hull form optimisation with Computational Fluid Dynamics

Aurélien Drouet, Erwan Jacquin, Pierre-Michel Guilcher

Page 2: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

Overview

Context

Software

Bulbous bow optimisation

Conclusions/perspectives

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Page 3: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

HydrOcean

Company specialised in marine CFD • Spinoff from Ecole Centrale Nantes Fluid Dyn. Lab.

• Expertise in 4 activity sectors of marine industry

• 20 high qualified CFD engineers

Efficient partnership with Bureau Veritas • Offer to BV clients advanced CFD services for specific applications

• Develop innovative & high level software, services, and

methodologies

A unique numerical towing tank • A unique range of numerical solvers

• Unlimited number of licences

• Large CPU power : use of around 100 to 200 cores for a standard

CFD study, access to over 2000 CPU cores

• Access to experimental facilities

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Page 4: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

HydrOcean

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Over 170 successful projects in six years …

Page 5: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

Numerical tools and solvers

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Our vision

1 - The accurate simulation of complex phenomena needs the use of

adapted solvers.

2 - The use of commercial CFD solver is cost and time consuming.

HydrOcean has access to unlimited license of in-house solvers

dedicated to marine applications and large CPU clusters.

3 - HydrOcean works in partnership with ECN Fluid Dyn. Lab. In the

development of unique solvers adapted to marine applications :

propeller model, incoming irregular waves …

Page 6: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

HydrOcean’s service for hull optimisation

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General hull shape parametric optimisation in resistance (curve section area, main hydrostatics )

Optimal trim angle evaluation for each draft and speed

Propulsion appendages

(rudder, shaft brackets …)

orientation and shape

optimisation

Bulbous bow shape parametric

optimisation. Total drag and

wave field reduction.

Bow or stern thrusters shape

optimisation.

• Orientation of level on flow

• Evaluation of Energy Saving

devices

Propeller design evaluation • Propulsive coefficients (Kt, Kq, hprop) • Cavitation inception • Pressure pulse

Stern, wedges, ducktail shape

optimisation in presence of

propeller ((1-t), (1-w), h hull )

Optimisation examples and potential associated gains

Page 7: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

OPTNAV : Parametric hull / appendages / propeller

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Parametric deformations • User defined deformation functions

• Coupled to Rhino grasshopper

Constraints • Hydrostatic calculations

• Curve section area

• Stability checks

Resistance calculations • Empirical formula

• CFD database

Automatic export of parametric hulls • CAD files : iges, 3dm, stl …

• Meshes : surface and 3D volume meshes

• Full automatic report Hull modeling software

dedicated to ship performance optimisation

Id

Del

taR

tm(%

)27

nds

0 20 40 60 80 100

-2

0

2

4

6

8InitDOE

MOGA

Parametric hull

modeling Automatic meshing Ship performance evaluation

Outputs:

l Resistance

l Ship power

l …

Deformation parameters :

l Bulbous bow

l Hull sections / shape

l Stern / Wedge …

Parametric exploration

Optimisation algorithms

Constraints :

l Hydrostatic

l Stability

l GA

Objectives :

l Resistance

l Ship power

l …

Optimisation process

Page 8: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

Main features

• Alessandrini et al. 1995

• Collaborative development ECN/BEC

• Extended validation for resistance predictions

• Free surface

• Non-linear conditions

• Free surface tracking

• Numerical scheme :

• RANS, implicite 2nd order FD shemes

• K-w turbulence model

• Fully coupled formulation (U V W P H)

• Topologies :

• Structured

• Multiblock

ICARE CFD solver

Page 9: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

ICARE CFD solver

Parallel Version

• MPI

• Large nonlinear system

• Blocking communications in preconditioner

• Typical cpu time: 4 hours x 4 cores

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Speed-up efficiency

Page 10: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

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CMA-CGM ships

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The Wheelhouse and the Engine Room of CMA CGM

• Managing the vessels

• Crew & Fleet

• DD

• Supply of spare parts and consumables

• Supervising New Buildings

• Providing CMA CGM with any technical advise

• Fleet Center Navigation

• Energy Department

Figures

• 108 vessels

• 606 197 TEUS capacity managed

• 4 142 seafarers

• 183 employees

Page 11: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

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Cost savings: action and technologies review

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Objective :

• Optimisation of bulbous bow during retrofit could be quite efficient if savings are proven

• Gains are higher if the vessels sails off-design conditions

Page 12: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

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Slow steaming for containerships

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Analyse :

• Daily mean speed evolution on a typical Asia to Europe trade since 2009

• Decrease from 24 knots down to a range of 12-18 knots

• Vessel initially optimized for 24.5 knots, 14m Draft

Initial design condition

Page 13: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

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Bulbous bow optimisation for operational profile

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850 RANSE-CFD computations

13600h cpu

12 15 18 21

9.5 3.0% 12.0% 10.5% 4.5%

12 2.5% 10.0% 8.8% 3.8%

13 3.0% 12.0% 10.5% 4.5%

14 1.5% 6.0% 5.3% 2.3%

Speed (knots)

Dra

ft (

m)

Objective : Optimisation of bulb for an operational profile of 17 conditions

Constraints : Conservation of max speed

Limitation of modifications so that box thruster section not modified

Conservation of LOA / LPP

Study performed at iso displacement and trim

Hull to be optimised for Operational profile (17 conditions)

Approach : parametric evaluation : 50 hull forms Direct deformations

Length

Width

Height

Coupled deformations based on

Width / height

Length height

Page 14: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

Bulbous bow optimisation for operational profile

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Analysis:

• Evaluation of all parameters

Length, Height, Width

• Specific and dedicated analysis tools for huge amount of data

Subvison for image comparison

Visual analysis

Specific developed routines

Initial

Optimal

Longer

Higher

Wider

Page 15: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

Bulbous bow optimisation for operational profile

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Analysis example: • Bulb width influence

The bulb’s width deformation has a strong influence on weighted Pe variation and a small influence on Pe at

Vmax

The thicker bulb offers 9.3% of gains on weighted Pe and 1.5% of loss on Pe at Vmax.

ID 22 ID 1 ID 7

Width increase

Page 16: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

Bulbous bow optimisation for operational profile

Page 16

Results :

• 9.4% gains on weighted Pe for a 1.5% loss on Pe at Vmax

ID 48 12 15 18 21 24Weighted Pe

variation (%)

9.5 -19.4% -22.4% -16.6% -10.1% / -18%

12 -19.7% -13.7% -9.5% -5.2% / -12%

13 -8.6% -8.3% -5.4% -2.4% / -6%

14 -5.0% -4.6% -2.6% -0.5% 1.5% -3%

-14.1% -13.3% -9.4% -5.1%Wegihted Pe

variation (%)

Speeds (knots)

Dra

ft (

m)

Initial Optimal

Dra

ft =

9.5

m

Dra

ft =

14 m

Initial Optimal

Dra

ft =

9.5

m

Dra

ft =

14 m

Page 17: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

Business Case

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Mean Consumption: 25,000 T/Year/vessel

Optimized Bulb: -9% in mean HFO Consumption

Savings : 2,250 T/Year/vessel (1,350,000 USD/Year/vessel)

Retrofit Cost

600,000 USD

ROI: 5-6 months

-800

-600

-400

-200

0

200

400

600

800

0 1 2 3 4 5 6 7 8 9 10 11 12

Month

Net Present Value

Cash flow (USD)

Gain cumulés (USD)

GO

Page 18: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

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CMA CGM TOSCA

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Work done during Dry Dock:

Propeller Boss Cap Fin

New Paint

Main Engine Overhauls

New Bulbous Bow

Page 19: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

CMA CGM TOSCA

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Sea trial after dry docks:

High savings for lower speeds

0

10

20

30

40

50

60

10 12 14 16 18 20 22 24

% MCR

Speed (knts)

TOSCA after DD + bulb

TOSCA before DD

TOSCA ST 13.4m

Puissance (TOSCA before DD)

Page 20: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

CMA CGM TOSCA

Page 20

Results from sea trial @13,4m

Speed (knts) 12 15 18 21 Average

Hydrodynamic gains

(PBCF + paint + Bulb) 27,3% 20,8% 8,1% 2,5% 14,7%

CMA CGM LA TRAVIATA

Speed (knts) 12 15 18 21 Average

Hydrodynamic gains

(PBCF + paint) 4,3% 8,7% 6,5% 8,3% 6,9%

Full scale sea trial accuracy : more than 2%

Hard to isolate single effect

Good agreement with computations

Vitesses (nds)

ID 48 12 15 18 21 24

T (m

)

9.5 -19.4% -22.4% -16.6% -10.1% /

12 -19.7% -13.7% -9.5% -5.2% /

13 -8.6% -8.3% -5.4% -2.4% /

14 -5.0% -4.6% -2.6% -0.5% 1.5%

CONCLUSION

Sister vessel same age, same Dry Dock, without bulb retrofit

Results from sea trial @13m

Page 21: Hull form optimisation with Computational Fluid Dynamics · Bulbous bow shape parametric optimisation. Total drag and wave field reduction. Bow or stern thrusters shape optimisation.

Expertise in Marine Hydrodynamics

Conclusions

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Original Bulbous bow was optimized for design conditions:

24.5 knots / 14m draft

Post crisis environment: need for flexibility and lower speeds

High savings expected from bulbous bow retrofitting

Computations done with accurate CFD codes

Parametric study to cover the whole range of deformations

Multi-criteria to cover the whole operating profile of the vessel

5 weeks study

Results confirmed by sea trials and first voyage of the vessel

Short time for return on investment

High cash flow generation

Following bulb retrofit a trim optimization study has been performed by

HydrOcean to update CMA CGM tables.